1. Field of the Invention
This invention relates to a device for separating heavier and lighter fractions of a fluid sample, and in particular a container containing a separator that provides such separation of blood upon centrifugation.
2. Description of Related Art
Diagnostic tests may require separation of a patient's whole blood sample into components such as serum or plasma (a lighter phase component) and red blood cells (a heavier phase component). Samples of whole blood are typically collected by venipuncture through a cannula or needle attached to a syringe or an evacuated collection tube. Separation of the blood into serum or plasma and red blood cells is then accomplished by rotation of the syringe or tube in a centrifuge. The tube or syringe generally contains a barrier that moves between the two phases upon centrifugation, and maintains that separation thereafter to allow subsequent examination of the individual components.
A variety of devices have been used in collection devices to divide the area between the heavier and lighter phases of a fluid sample. The most widely used devices include thixotropic gel materials such as polyester gels in a tube. These devices require special manufacturing equipment to prepare the gel and to fill the tubes. Moreover, the shelf-life of the product may be limited because over time, globules of gel may be released from the gel mass. These globules may enter the serum sample gel and may be released from the gel mass. These globules may enter the serum sample and thereby clog the measuring instruments. Such clogging can lead to considerable downtime for an instrument. In addition, no commercially available gel is completely chemically inert to all analytes. If certain drugs are present in the blood sample when it is taken, there can be an adverse chemical reaction with the gel.
Therefore, a need exists for a separator device that avoids the problems of gels. Such a device advantageously exhibits one or more of the following properties: (i) easily used to separate a blood sample; (ii) largely unaffected by temperature during storage and shipping; (iii) stable to radiation sterilization; (iv) employs the benefits of a thixotropic gel barrier yet avoids the disadvantages of placing a gel in contact with the separated blood components; (v) reduces cross contamination of the heavier and lighter phases of the sample during centrifugation; (vi) reduces adhesion of the lower and higher density materials against the separator device; (vii) able to move into position to form a barrier in less time than conventional methods and devices; (viii) able to provide a clearer specimen with less cell contamination than conventional methods and devices; and (ix) able to be used with standard sampling equipment.